Carbon dioxide (CO.sub.2) and/or water removal from gaseous streams can be an essential process in many systems. In industry, purification of input gases for oxygen rich processes, such as a fuel cell system, is important. In enclosed environments, the removal of CO.sub.2 can be critical.
Absorbents, such as soda lime, which react with the CO.sub.2, are commonly utilized for this application. However, this process is only satisfactory for short term applications due to the irreversible nature of the reaction. For long term durations, regenerable sorbents were developed, such as an amine solution system. However, this solution is impractical in conditions of less than 0.2 volume percent CO.sub.2 in air, has limited life due to amine solution decomposition, and is impractical for use in microgravity applications.
Improved regenerable sorption systems are disclosed in U.S. Pat. Nos. 3,511,595, 3,865,924, and 4,822,383. U.S. Pat. No. 3,511,595 teaches removing CO.sub.2 and water vapor from air by reacting with potassium carbonate, forming potassium bicarbonate, with control temperatures ranging from 40.degree. F. to 100.degree. F. The bed is regenerated at somewhat over 200.degree. F.
U.S. Pat. No. 3,865,924 teaches utilizing a regenerable absorbent, composed of a mixture of finely divided alkali metal carbonate and alumina, which absorbs faster than pure carbonate alone. The sorption occurs at room temperature or slightly above (up to about 140.degree. F.), while regeneration is preferably run at high temperatures up to about 300.degree. F.
The utilization of a regenerable solid amine system is taught by U.S. Pat. No. 4,822,383. The process includes utilizing a plurality of beds, each having three states, adsorption state wherein the bed adsorbs the CO.sub.2 from the air, desorption state wherein steam desorbs the CO.sub.2 from the bed, and dewatering state wherein the condensate is removed from the bed.
Due to the expanded use of enclosed environments, what is needed in the art is a regenerable CO.sub.2 /H.sub.2 O sorbent with extended cycle life.